284 ARTHUR WILLIAM MEYER. 



'03, also found that intrauterine death and retrogression of the 

 guinea pig fetus can be effected experimentally through various 

 means, and according to Koebner, '10, not merely ova or young 

 fetuses are absorbed, but even the bones of older ones disappear 

 completely under experimental conditions in the rabbit. It 

 would seem unlikely, however, that such could be the case in 

 any but the very earliest stages in the development of the skeleton 

 for a considerable degree of acidity would have to develop in 

 order to make this possible. Since it is believed that the develop- 

 ment of acidity not only is slow but also slight in embryonic 

 tissues, Koebner's conclusion regarding the bones seems to be 

 open to some doubt. Wiener, '05, also found that autolysis is 

 very slight in tissues with an alkaline reaction and that a slight 

 increase in acidity greatly accelerates it. 



Fraenkel, '10, extended and confirmed his work done in '03 

 by a very large series of experiments touching various phases of 

 the corpus luteum problem and among other things concluded 

 that one corpus luteum can protect at least three ova sufficiently 

 to insure continued development. 



Although the ova found by Huber, '15, were very young, 

 the significance of the facts would seem to be similar. Likewise 

 Mall, '15, while writing "On the fate of the human embryo in 

 tubal pregnancy," stated that "we have no data on the number 

 of ova which disintegrate early, but the study of comparative 

 embryology warrants the conclusion that many young ova 

 degenerate and disintegrate. I am informed by Dr. Huber, who 

 has studied with great care much material among rats, that some 

 of the fertilized ova break down before implantation. The 

 same seems to be true regarding the pig. We usually find more 

 corpora lutea in the ovaries than embryos in the uterus, indi- 

 cating that all of the ova do not produce normal embryos." 

 Similar phenomena also were reported by Meyer, '17, in regard 

 to young conceptuses in the guinea pig. Curtis, '15, also re- 

 ported the absorption of ova in guinea pigs in consequence of 

 the injection of extracts of the human placenta, but unfortun- 

 ately did not give convincing evidence regarding his knowledge 

 of the presence of pregnancy in the animals concerned, and did 

 not make a microscopic examination. Since Curtis stated that 



